<HTML>
<CENTER><A HREF = "http://sparta.sandia.gov">SPARTA WWW Site</A> - <A HREF = "Manual.html">SPARTA Documentation</A> - <A HREF = "Section_commands.html#comm">SPARTA Commands</A> 
</CENTER>






<HR>

<H3>compute react/isurf/grid command 
</H3>
<P><B>Syntax:</B>
</P>
<PRE>compute ID react/isurf/grid group-ID reaction-ID value1 value2 ... 
</PRE>
<UL><LI>ID is documented in <A HREF = "compute.html">compute</A> command 

<LI>react/isurf/grid = style name of this compute command 

<LI>group-ID = group ID for which grid cells to perform calculation on 

<LI>reaction-ID = surface reaction ID which defines surface reactions 

<LI>zero or more values can be appended 

<LI>value = <I>r:s1/s2/s3 ...</I> or <I>p:s1/s2/s3 ...</I> 

<PRE>  r: or p: = list of reactant species or product species
  s1,s2,s3 = one or more species IDs, separated by "/" character 
</PRE>

</UL>
<P><B>Examples:</B>
</P>
<PRE>surf_react air prob air.surf
compute 1 react/isurf/grid all air
compute 2 react/isurf/grid all air r:N/O/N2/O2 p:N/O/NO 
</PRE>
<P>These commands will dump time averages for each surface element to a
dump file every 1000 steps:
</P>
<PRE>compute 2 react/isurf/grid all air r:N/O/N2/O2 p:N/O/NO
fix 1 ave/grid all 10 100 1000 c_2[*]
dump 1 grid all 1000 tmp.surgrid id f_1[*] 
</PRE>
<P><B>Description:</B>
</P>
<P>Define a computation that tallies counts of reactions for each grid
cell containing implicit surface elements in a grid group, based on
the particles that collide with those elements.  Only grid cells
elements in the grid group specified by <I>group-ID</I> are included in the
tallying.  See the <A HREF = "group.html">group grid</A> command for info on how
grid cells can be assigned to grid groups.  Likewise only grid cells
with surface elements assigned to the surface reaction model specified
by <I>reaction-ID</I> are included in the tallying.
</P>
<P>Implicit surface elements are triangles for 3d simulations and line
segments for 2d simulations.  Unlike explicit surface elements, each
triangle or line segment is wholly contained within a single grid
cell.  See the <A HREF = "read_isurf.html">read_isurf</A> command for details.
</P>
<P>This command can only be used for simulations with implicit surface
elements.  See the similar <A HREF = "compute_react_surf.html">compute
react/surf</A> command for use with simulations
with explicit surface elements.
</P>
<P>Note that when a particle collides with a surface element, it can
bounce off (possibly as a different species), be captured by the
surface (vanish), or a 2nd particle can also be emitted.
</P>
<P>The doc page for the <A HREF = "surf_react.html">surf_react</A> command explains the
different reactions that can occur for each specified style.
</P>
<P>If no values are specified each reaction specified by the
<A HREF = "surf_react.html">surf_react</A> style is tallied individually for each
grid cell.
</P>
<P>If M values are specified, then M tallies are made for each grid cell,
one per value.  If the value starts with "r:" then any reaction which
occurs with one (or more) of the listed species as a reactant is
counted as part of that tally.  If the value starts with "p:" then any
reaction which occurs with one (or more) of the listed species as a
product is counted as part of that tally.  Note that these rules mean
that a single reaction may be tallied multiple times depending on
which values it matches.
</P>
<P>The results of this compute can be used by different commands in
different ways.  The values for a single timestep can be output by the
<A HREF = "dump.html">dump grid</A> command.
</P>
<P>The values over many sampling timesteps can be averaged by the <A HREF = "fix_ave_grid.html">fix
ave/grid</A> command.  
</P>
<HR>

<P><B>Output info:</B>
</P>
<P>This compute calculates a per-grid array, with the number of columns
either equal to the number of reactions defined by the
<A HREF = "surf_react">surf_react</A> style (if no values are specified) or equal to
M = the # of values specified.
</P>
<P>Grid cells not in the specified <I>group-ID</I> or whose implicit surfaces
are not assigned to the specified <I>reaction-ID</I> will output zeroes for
all their values.
</P>
<P>The array can be accessed by any command that uses per-grid values
from a compute as input.  See <A HREF = "Section_howto.html#howto_4">Section 6.4</A>
for an overview of SPARTA output options.
</P>
<P>The per-grid array values are counts of the number of reactions that
occurred on surface elements in that grid cell.
</P>
<HR>

<P><B>Restrictions:</B> none
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "fix_ave_grid.html">fix ave/grid</A>, <A HREF = "dump.html">dump grid</A>, <A HREF = "compute_react_surf.html">compute
react/surf</A>
</P>
<P><B>Default:</B> none
</P>
</HTML>
